can not use conditions in ggplot with position arguments

I want to set positon with some conditions, but an error occured when I use if_else().

A reproducible example is below.

My question is :

How can I use conditions in position in ggplot2.

library(dplyr)

pd_ture = position_dodge(.4)
pd_false = position_dodge(.6)

mtcars_true = mtcars %>% mutate(test = TRUE)
mtcars_false =mtcars %>% mutate(test = FALSE)


ggplot(mtcars_true, aes(factor(cyl), fill = factor(vs)))  
  geom_bar(position = if_else(unique(mtcars_true$test), pd_ture, pd_false))

# Error in true[rep(NA_integer_, length(condition))] : 
#  object of type 'environment' is not subsettable

ggplot(mtcars_false, aes(factor(cyl), fill = factor(vs)))  
  geom_bar(position = if_else(unique(mtcars_false$test), pd_false, pd_ture))

# Error in true[rep(NA_integer_, length(condition))] : 
#  object of type 'environment' is not subsettable

CodePudding user response：

You can do this, but not with if_else or ifelse, since they will apply the subsetting operator to the output of position_dodge, which is not subsettable. Instead, you need a good old-fashioned if(unique(mtcars_true$test)) pd_ture else pd_false:

ggplot(mtcars_true, aes(factor(cyl), fill = factor(vs)))  
  geom_bar(position = if(unique(mtcars_true$test)) pd_ture else pd_false)

CodePudding user response：

I don't think you can do that. What you want is a pattern like this:

ggplot(mtcars_true, aes(factor(cyl), fill = factor(vs)))  
  geom_bar(data = . %>% filter(test), position = pd_ture)  
  geom_bar(data = . %>% filter(!test), position = pd_false)

But the way you set it up, the mtcars_true/mt_cars_false is not really made for this. So to make the current setup work, you need:

ggplot(mtcars_true, aes(factor(cyl), fill = factor(vs)))  
  geom_bar(data = mtcars_true, position = pd_ture)  
  geom_bar(data = mtcars_false, position = pd_false)

But the pattern of data = . %>% [data transforming pipes] will allow you to subset which part of the data the current layer / geom_* is being fed.